$ { {-3} \times \left[\begin{array}{rrr}{3} & {-2} & {-1} \\ {2} & {0} & {4}\end{array}\right] = {?} } $
Explanation: To multiply a matrix by a number, multiply each item of the matrix by the number. ${\left[\begin{array}{rrr}{-3}\times{3} & {-3}\times{-2} & {-3}\times{-1} \\ {-3}\times{2} & {-3}\times{0} & {-3}\times{4}\end{array}\right]}$ Now, simplify: ${\left[\begin{array}{rrr}{-9} & {6} & {3} \\ {-6} & {0} & {-12}\end{array}\right]}$